Primarily for use in component transfer apparatuses for handling components such as an electronic component, manufacturing apparatuses for manufacturing a semiconductor device, a liquid-crystal display device and others, etc., applications of a linear motor have been increasing year by year. Particularly, in late years, there has been a growing need for a thin-shaped high-performance linear motor. To meet such a need, a linear motor, such as a linear motor LM having a structure illustrated in FIGS. 18 and 19 (the following Non-Patent Document 1), has been proposed.
FIGS. 18 and 19 show one example of a conventional linear motor, wherein FIG. 19 is a sectional view taken along the arrowed line XIX-XIX in FIG. 18. In the following illustrative figures, XYZ rectangular coordinate axes on the basis of a linear motor LM are shown therein in order to clarify a directional relationship in each of the figures. Among the three directions X, Y, and Z, a moving direction to be set for the linear motor LM, a widthwise direction of the linear motor LM, and a frontward-rearward direction of the linear motor LM, are indicated by Z, Y, and X, respectively. Also, the signs (+, −) in each of the rectangular coordinate axes indicate a frontward side (+X side), a rearward side (−X side), a one edge side (−Y side), the other edge side (+Y side), a forward side (−Z side) and a backward side (+Z side), in the directions X, Y, and Z, for descriptive purposes.
The linear motor LM illustrated in FIGS. 18 and 19 comprises two linear guides 2A, 2B on a base plate 1. Each of the linear guides 2A, 2B has a linear-shaped rail 2a and a slider 2b, wherein the two rails 2a are provided parallel to each other along the moving direction Z while being spaced apart from each other in the widthwise direction Y, and the two sliders 2b are provided slidably along respective ones of the rails 2a in the moving direction Z. An armature 3 is provided between the linear guides 2A, 2B configured as above. The armature 3 is comprised of a plurality of densely-wound coils provided on a surface of the base plate 1 with intervals along the moving direction Z while allowing each axial core to extend along the widthwise direction Y. This armature 3 forms a stator of the linear motor LM.
Also, a plate-shaped movable base 4 having a width (length in the widthwise direction Y) equal to that of the base plate 1 is attached to both upper surfaces of the sliders 2b, so that it is adapted to be movable along the moving direction Z at a position above the base plate 1. In this manner, the movable base 4 and the two sliders 2b are adapted to be integrally movable along the moving direction Z as a “movable section”.
Two yokes 5A, 5B, each having a permanent magnet array attached thereto on a respective one of opposite sides of the armature 3 along the widthwise direction Y, are attached to a rear surface of the movable base 4 to serve as a mover. Although the specific illustration is omitted, each of the yokes 5A, 5B extends in a direction perpendicular to the drawing sheet of FIG. 19, i.e., in the moving direction Z. Along with the extending direction Z of the yoke 5A (5B), plurality of permanent magnet arrays 6A and 6B are provided between the yokes 5A and 5B and the armature 3. An upper end of the yoke 5A is attached to the rear surface of the movable base 4 to allow the permanent magnet array 6A to face the armature 3 from the other edge side (+Y side) in the widthwise direction Y, and the yoke 5B is attached to the rear surface of the movable base 4 to allow the permanent magnet array 6B to face the armature 3 from the one edge side (−Y side) in the widthwise direction Y. Thus, through an operation of controlling a current to be applied to the coils of the armature 3, the movable base 4 is linearly driven in the direction Z by interaction of magnetic fluxes generated between the stator (armature 3) and the permanent magnet arrays 6A, 6B of the mover.
A detector unit 7 for detecting a position of the movable base 4 is provided on a side opposite to the mover in the widthwise direction Y (on the +Y side) with respect to the linear guide 2A. More specifically, a sensor 7a is fixedly disposed on an upper surface of the base plate 1, and a linear scale 7b is attached to a lower surface of the movable base 4 to face the sensor 7a. In this manner, the sensor 7a and the linear scale 7b are disposed opposed to each other, so that the linear motor LM can detect a position of the movable base 4 in the direction Z.
In the conventional linear motor LM, as shown in FIG. 19, the linear guide 2A, yoke 5A, the permanent magnet array 6A, the armature 3, the permanent magnet array 6B, the yoke 5B, and the linear guide 2B are arranged in the widthwise direction Y between the base plate 1 and the movable base 4, to facilitate a reduction in depth dimension of the linear motor LM (in apparatus size in the frontward-rearward direction X), as compared with a type where the armature, the permanent magnet array, the yoke and the movable base are arranged in a frontward-rearward direction with respect to the base plate. Also, the sliders 2b, the yokes 5A, 5B and the permanent magnet arrays 6A, 6B are integrally fixed to the movable base 4 to allow them to be moved back and forth along the moving direction Z with respect to the rails 2a and the armature 3 fixed to the base plate 1.
Non-Patent Document 1: Hitoshi Yamamoto, “Materials/Electronic Materials Topics 32nd Development of World's Thinnest 7 mm-Thickness Linear Motor”, [online], Dec. 11, 2006, Japan Electronics and Information Technology Association, [search: Dec. 10, 2007], Internet <http://home.jeita.or.jp/ecb/material/No032.html>